Rebar Corrosion Research Articles

Review on Rebar Corrosion in Alkali-Activated Concrete Subjected to Chloride-Rich Environment

Review on Rebar Corrosion in Alkali-Activated Concrete Subjected to Chloride-Rich Environment

Anti-corrosive superhydrophobic coatings for reinforcement protection: recycling of concrete garbage

PurposeThe purpose of this paper was to prepare a ternary hierarchical rough particle to accelerate the anti-corrosive design for coastal concrete infrastructures.Design/methodology/approachA kind of micro-nano hydrophobic ternary microparticles was fabricated from SiO2/halloysite nanotubes (HNTs) and recycled concrete powders (RCPs), which was then mixed with sodium silicate and silane to form an inorganic slurry. The slurry was further sprayed on the concrete surface to construct a superhydrophobic coating (SHC). Transmission electron microscopy and energy-dispersive X-ray spectroscopy mappings demonstrate that the nano-sized SiO2 has been grafted on the sub-micron HNTs and then further adhered to the surface of micro-sized RCP, forming a kind of superhydrophobic particles (SiO2/HNTs@RCP) featured of abundant micro-nano hierarchical structures.FindingsThe SHC surface presents excellent superhydrophobicity with the water contact angle >156°. Electrochemical tests indicate that the corrosion rate of mild steel rebar in coated concrete reduces three-order magnitudes relative to the uncoated one in 3.5% NaCl solution. Water uptake and chloride ion (Cl-) diffusion tests show that the SHC exhibits high H2O and Cl- ions barrier properties thanks to the pore-sealing and water-repellence properties of SiO2/HNTs@RCP particles. Furthermore, the SHC possesses considerable mechanical durability and outstanding self-cleaning ability.Originality/valueSHC inhibits water uptake, Cl- diffusion and rebar corrosion of concrete, which will promote the sustainable application of concrete waste in anti-corrosive concrete projects.

Assessing the effect of sodium nitrite as corrosion inhibitor against the corrosion of steel rebar in alkali-activated concrete

The aim of this study is to investigate the effectiveness of corrosion inhibitor against chloride-induced corrosion of steel rebar in fly-ash (FA) and GGBS (ground granulated blast furnace slag) and Nanofine-based alkali-activated concrete. The Alkali-Activated Concrete (AAC) was prepared from FA, ground granulated blast furnace slag (GGBS), and Nanofine with Sodium hydroxide (NaOH) and Sodium Silicate (Na2SiO3) solutions. The concentration of NaOH varies to 10 M, 12 M, and 14 M, and all the specimens were subjected to accelerated corrosion, to perform the non-destructive test after the corrosion of the steel rebars. Fourier Transform Infrared (FTIR), scanning electron microscope (SEM), Energy dispersive X-ray spectroscopy (EDS), and Electron Backscatter Diffraction (EBSD) were used to examine the microstructure of AAC in the presence of Nano-Fine GGBS (NF), Sodium Chloride (NaCl), and NaNO2 and to compare the strength and corrosion properties with AAC and OPC. The ratio of sodium silicate to sodium hydroxide was taken as 2.5 and the solution-to-binder ratio was taken as 0.5. The compressive strength and ultrasonic pulse velocity (UPV) test of the Nano-fine based alkali-activated concrete increases as compared to the control concrete. The increase in the dosages of corrosion inhibitor and nano-fine increases the compressive strength of the control concrete and alkali-activated concrete. The half-cell potential of the control concrete and nano fine admixed with alkali-activated concrete mixes with different molarities is uncertain. The increases in the dosages of corrosion inhibitors reduce the occurrence of corrosion in the steel reinforcement rebars.

Mechanism of rebar depassivation in concrete containing sulphate: A vicious cycle between sulphate adsorption and surface vacancy formation

Sulphate-induced corrosion of rebars has been reported to plague the lifespan of concrete structures. However, the associated mechanism underlying this issue is still unclear and therefore deserves further investigation. To fill in this gap, three electrochemical experiments including OCP, EIS and LPR were conducted in this study, alongside XPS and SEM characterizations. Moreover, a Density Functional Theory (DFT) was adopted to simulate the depassivation behaviour of rebar under the sulphate condition. Taking together, the underlying mechanism was disclosed. The results reveal that the presence of sulphate ions appeared to reduce the thickness of the rebar passive film and the Fe3+/Fe2+ ratio in the outer layer. In addition, the threshold value of [SO42−]/[OH−] to cause the depassivation of rebar was experimentally found about 1.26–1.51 in the saturated Ca(OH)2 solution. Further, the pristine and vacancy-contained α-Fe2O3 (001) surfaces were chosen respectively, to simulate the passive film surface surrounding rebars via DFT. It was found that the SO42− adsorption boosted the formation of surface vacancy, and compared to the pristine surface, the increase in SO42− coverage also promoted the ensuing formation of Fe vacancy on the O vacancy-contained surface. Then, the Fe-O pair vacancy was so formed, and in turn, boosted the following adsorption of SO42− on the passive film of rebars. Combining the experimental results and DFT simulation, the vicious cycle is believed to exist during the sulphate-induced depassivation of rebar, specifically composed of (i) the adsorption of SO42−, (ii) the vacancy formation and increase, and (iii) the progressively enhanced adsorption of SO42−.

Predicting corrosion behaviour of steel reinforcement in eco-friendly coral aggregate concrete based on hybrid machine learning methods

ABSTRACT This study proposes a machine learning-assisted method for assessing steel reinforcement corrosion, utilising data on chloride ion concentration (CIC) and chloride ion concentration threshold (CCT) from eco-friendly coral aggregate concrete (EFCAC). A total of 2185 data points were collected to establish the EFCAC-CIC database. A multi-objective slime mould optimised support vector regression (MOSMA-SVR) model for EFCAC-CIC was developed. The significance of each feature to EFCAC-CIC was analysed. Subsequently, a graphical user interface (GUI) was developed based on the MOSMA-SVR model. Finally, the GUI and EFCAC-CCT were used to assess the corrosion behaviour of reinforcement. Results indicate that the MOSMA-SVR model provides predictions that are closer to the actual values, with smaller mean errors and standard deviations. The performance indicators, including coefficient of determination, mean absolute error, mean absolute percentage error, mean square error, root mean square error, and a20-index, of the MOSMA-SVR model are 0.987, 0.0124, 0.0332, 2.91e − 4, 0.0171 and 0.9991, respectively, and they are superior to those of the other tested models. The water type and the water–binder ratio are identified as the two most critical factors. Furthermore, by integrating the GUI and feature importance analysis results, chloride salt-resistant EFCAC can be designed. When this is combined with the GUI and EFCAC-CCT, the corrosion of rebar in EFCAC can be assessed in real time.

Permittivity analysis of weathered concrete in a bridge based on open-ended probe and impedance measurements

Pathologies like corrosion of rebars or alkali aggregate reactions in a reinforced concrete (RC) bridge are usually accompanied by the existence of aqueous pore solutions with a high concentration of ions. The distribution of aqueous solutions in the concrete is inhomogeneous and depends on the RC’s location in the bridge and complex climate factors. Frequency-dependent complex permittivity is sensitive to aqueous pore solutions because the high conductivity caused by charge carriers can result in a large imaginary part of the permittivity, much higher than that caused by water. In this study, we used a non-destructive open-ended probe to measure the complex permittivity of the RC in a bridge’s pillar with different levels of pathologies. By measuring the impedance of core samples with various controlled water volumetric fractions in the laboratory, the water effect on the evolution of the loss tangent (the ratio between the imaginary part of the permittivity and the real part) can be calibrated. Comparing the loss tangent in the bridge with that of the core samples treated by water, we can map the areas with a high density of aqueous pore solution and cracks, and estimate the unhealthy area with partial damage in the pillar by an effective and non-destructive diagnosis.

Application of Digitised Frequency Modulated Thermal Wave Imaging for Testing and Evaluation of Rebar Corrosion in Concrete Structures: A Numerical Study

Application of Digitised Frequency Modulated Thermal Wave Imaging for Testing and Evaluation of Rebar Corrosion in Concrete Structures: A Numerical Study

Study Of The Impact Of Several Coatings In Minimizing The Rebar Corrosion In Concrete

This paper represents experimental study to examine the influence of several coatings to decrease the rebar corrosion. The experiments were carried out for three types of coatings. Those have been painted on the steel and select the best type of coatings in decreasing the steel corrosion rate. Testing program included experiments to select the best one within three types of coatings (Isonem MS Polymers, Sika Zink Rich-1, Isonem PU Floor) are used and available in market. The result of corrosion rate for rebar in uncoated samples in level five (after 70 days) was loss of more than 50% from its weight. While, the result of corrosion rate for rebar in samples with coating type (C) ”Isonem PU Floor” was loss of less than 2% from its weight which is the most effective type and the best coating.

Effects of electroless nickel -coating on tribological and corrosion behaviour of TMT steel rebar with multi-walled carbon-nanotube and titanium dioxide nanoparticles

This study incorporated Multi-walled carbon nanotube particles (MWCNTs) and Titanium Dioxide Nanoparticles (TiO2) into a metal matrix composite in Ni–P coated substrate using an Electroless technique. This study significantly improves the tribological properties, enhances corrosion resistance, increases durability and extends the service life of coated rebar. Coated rebar helps make infrastructure more sustainable by extending the life of buildings and lowering their material consumption, trash output, and ecological footprint. The tribological behaviour of steel rebar has been studied by using a variety of characterization techniques, like X-ray diffraction, Atomic Force Microscopy, Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (EDX) including the corrosion test and the hardness test. The topographical roughness of the bare specimen, Ni–P coated specimen, CNT coated specimen and TiO2 coated specimen are 67.4 nm, 112 nm, 201 nm, and 162 nm respectively. The microhardness of the bare substrate, Ni–P coated, CNT doped coated, and TiO2 dopped coated specimens was done using Vicker's Hardness tester and the mean values were 455 HV, 580 HV, 810 HV, and 680 HV respectively. Resistance to corrosion of TMT steel rebar of Fe500 was examined using the polarisation method and Electrochemical-Impedance-Spectroscope (EIS) method. These techniques were examined in 3.5 wt% aqueous medium of NaCl and analysed the Ecorr (corrosion potential) and Icorr (Corrosion current density) of the bare substrate, Ni–P coated, Ni–P/CNT and Ni–P/TiO2 substrate. The corrosion inhabitation efficiency of the Ni–P-CNT doped was 22.5% more than the Bare substrate, and the TiO2 doped coated specimen was 10.63% more than the bare substrate. Resistance to corrosion of the CNT-coated substrate is better than Ni–P/TiO2 and Ni–P-coated specimens.

Effect of loading level on the corrosion resistance of a novel self-healing cementitious composite

A novel self-healing cementitious composite SMA-ECC is utilized to enhance corrosion resistance and maintain mechanical properties in chloride environment. The purpose of this study is to investigate the impact of the loading level on embedded steel rebar corrosion and the self-healing performance of SMA-ECC. The study examined the damage conditions, mechanical properties, and rebar corrosion resistance following a loading test. Chloride ingress depth and electrochemical tests were adopted to evaluate the corrosion resistance of the specimens. The findings reveal that SMA-ECC exhibits remarkable self-healing abilities in terms of damage recovery and restoration of mechanical properties. Cracks smaller than 50 μm can achieve a 100 % closure rate in SMA-ECC. It was observed that specimens with less damage (50 %, 70 % damage conditions) displayed improved chloride resistance (SMA-ECC in 50 % damage condition has equivalent corrosion resistance in terms of corrosion current density compared to intact NC control specimens), leading to higher corrosion resistance for SMA-ECC according to the electrochemical test results.

Analysis of the Effectiveness of the Application of Corrosion Inhibitors to Steel Re-Bars Embedded in Concrete

Reinforced concrete is the most widely used material in the construction of building structures, being noted for its versatility and low cost. However, the durability of reinforced concrete structures can be compromised by the corrosion of steel re-bars, especially in the presence of chlorides. To address this challenge and promote sustainability, the use of corrosion inhibitors has been researched as a way to extend the lifespan of structures. This study assessed the effectiveness of using a commercial corrosion inhibitor on steel re-bars embedded in types of concrete with different chloride percentages, using electrochemical methods to measure the corrosion rate and potential. The results indicate that, in the absence of corrosion inhibitors, corrosion rates become unacceptable with chloride percentages equal to or higher than 0.8% by weight of cement. The application of inhibitors significantly reduced the corrosion rate, particularly at chloride percentages of 0.8% and 1.2%, maintaining the re-bars in a passive state or at moderate levels of corrosion. However, for chloride percentages higher than 1.6%, high levels of corrosion were observed, even in the presence of inhibitors. The findings suggest that the use of inhibitors can be an effective strategy in preventing corrosion in reinforced concrete structures, contributing to their structural integrity and long-term sustainability.

Fundamental Properties of Sub-THz Reflected Waves for Water Content Estimation of Reinforced Concrete Structures

Water plays a significant role in the deterioration of reinforced concrete buildings; therefore, it is essential to evaluate the water content of the cover concrete. This study explores a novel non-destructive method for assessing the water content using sub-terahertz (sub-THz) waves. Among the four frequencies selected to evaluate the water content, an increase in reflectance was observed as the unit volume water content increased, and smaller data scatter was confirmed as the frequency increased. The derived empirical equation can classify the corrosion risk of the rebar environment based on the water content obtained using reflectance measurements. In other words, it can contribute to the diagnosis of the building integrity associated with rebar corrosion.

تأثير تأكل حديد التسليح المعرض في الخرسانة المسلحة لمياه المحلية لمدينة طرابلس

In this research, we study the rate of corrosion of rebar for beams and cubes within the climatic environment (Climatic chamber Environment) (C.C.E) using a concrete cover ranging from (25 to 65) mm with changing the ratio of water to cement by percentages ranging from (0.45 to 0.75) mm using local water (tap water T.T.W) for the city of Tripoli and show that these samples are affected in terms of the rate of corrosion and electrochemical behavior according to changing the proportions of water to cement as well as changing the proportions of concrete cover. The research came as an integral part of what we presented in a previous study[1] . In it, we presented the results obtained after exposing beams and cubes outside the outdoor environment to different conditions using local water. Keywords: Concrete cover – corrosion- reinforced concrete- tap water- Climatic Chamber Environment

Corrosion of Steel Rebars in Construction Materials with Reinforced Pervious Concrete

Pervious concrete has great potential for use in many practical applications as a part of urban facilities that can add value through water harvesting and mitigating severe damage from floods. The construction and agricultural industries can take direct advantage of pervious concrete’s characteristics when water is a key factor included in projects as part of the useful life of a facility. Pervious concrete also has applications in vertical constructions, fountains, and pedestrian crossings. This work evidences that pervious concrete’s corrosion current increases with increasing aggregate size. Also, corrosion is a factor to consider only when steel pieces are immersed, aggravated by the presence of chlorine, but it drains water and does not retain moisture. Steel-reinforced pervious concrete was studied, and the grain size of the inert material and the corrosion process parameters were investigated. The electrochemical frequency modulation technique is proposed as a suitable test for a fast, reproducible assessment which, without damaging reinforced cement structures, particularly pervious concrete, indicates a trend of increasing corrosion current density as the size of the aggregate increases or density diminishes.

Experimental investigation of flexural bond behavior of sand-coated GFRP rebar embedded in concrete

Steel rebars used in Reinforced Concrete (RC) elements may be subjected to corrosion due to aggressive environmental conditions. Rebar corrosion reduces the durability and the structural capacity of RC elements. On the other hand, since the steel rebars affect the magnetic fields, it is not preferred to be used in RC structures which is used to carry the equipment that propagate magnetic waves such as toll plazas on highways. For these reasons, the use of Fiber Reinforced Polymer (FRP) rebars is increasing, especially in RC infrastructure constructions. The objective of the present study is to investigate the bond behavior of Glass Fiber Reinforced Polymer (GFRP) rebar with a sand-coated outer surface in concrete using the arched beam test method. The concrete strength and the embedment length were chosen as variable parameters and 34 beam test specimens were tested in the laboratory. A comparative analysis of the crack patterns, the diagonal crack angles and the failure modes of the specimens is made. In addition, the experimentally determined bond-slip relationships were compared with different analytical models in the literature. Consequently, a bond-slip model, which takes into account CMR (Cosenza-Manfredi-Realfonzo) for the increasing part and mBPE (modified Bertero-Popov-Eligehausen) for the decreasing part, is proposed to be used in the numerical models of RC beams with sand-coated GFRP rebars. A prediction model for the bond strength is proposed, along with a recommendation for an upper bound value for the bond stress, which indirectly offers a minimum embedment length for a bond without slippage.

A novel LDHs-VB3- inhibitor for rebar corrosion in simulated concrete pore solution: Synthesis, performance and mechanism

Developing novel chloride-trapping inhibitors is of great significance for enhancing the durability of marine concrete structures. In this study, a novel LDHs-VB3- inhibitor was synthesized through the ion exchange method. Then, the corrosion inhibition mechanism of LDHs-VB3- inhibitor for rebar in the whole process of release - capture - adsorption - retardation was studied using experiments and density functional theory (DFT) simulations. The chloride ion exchange test demonstrates that the LDHs-VB3- inhibitor has a chloride trapping capacity of 35.5 mg/g in the saturated Ca(OH)2 solution containing 0.14 M NaCl, implying that it could capture Cl- in concrete pore solution. According to the electrochemical tests, the critical chloride concentration of rebar in the simulated concrete solution containing LDHs-VB3- falls within a range of 0.22 M–0.28 M, which is much higher than that in the solution without LDHs-VB3- (0.10 M–0.14 M). DFT simulations indicate that LDHs-VB3- exhibits more positive binding energy and uneven binding forces in contrast to LDHs-Cl-. Consequently, VB3- could be easily replaced by Cl- and then released into the pore solution of concrete. Moreover, the released VB3- could adsorb on the α-Fe2O3 surface in a concrete environment via the interaction of surface Fe atoms with N and O atoms of VB3-. The preadsorbed VB3- could diminish the interaction of Cl- with the α-Fe2O3 surface by reducing electron transfer, thereby mitigating the risk of passive film breakdown and retarding the chloride-induced corrosion of rebars.

Capacity assessment of uncorroded and corroded dapped‐end beams by NLFE and strut‐and‐tie based methods

AbstractThe verification of dapped‐end beams degraded by corrosion is a problem, especially for existing bridges in service. This paper proposes a nonlinear finite element (NLFE) modeling procedure and a simple strut‐and‐tie based procedure for predicting the response of dapped‐end beams subjected to chloride corrosion. Firstly, the finite element modeling strategy, based on the adoption of multilayer shell elements and the PARC_CL 2.1 crack model is described. Then, the degradation effects on concrete, rebars, and steel‐to‐concrete interaction are defined as a function of the propagation period of corrosion. In particular, the effects of corrosion on the reinforcement are modeled by applying a reduction of tensile strength that considers for both the reduction of cross‐section and the ultimate strain caused by pitting. Concrete splitting cracking due to volume expansion during rust formation is modeled by reducing the mechanical properties of concrete. Corrosion effects in steel‐to‐concrete interaction are modeled by applying a bond strength decay to the spring elements connecting corroded rebars—modeled with truss elements—and concrete multilayer shell elements. The proposed finite element procedure is used to study two scenarios based on different spatial distributions of corrosion‐prone areas. Subsequently, a simplified analytical approach based on the strut‐and‐corroded tie method—called S&CT method—is proposed and compared with the finite element outcomes. Finally, the validations of the two proposed methods are presented with respect to a corroded dapped‐end beam, showing that corrosion of rebars affects the resistance mechanisms of the dapped‐end beam, by reducing both resistance and ductility. The proposed simplified analytical S&CT method provides conservative and safe results compared to the numerical NLFE model and to experimental data.

Numerical Simulation of Deterioration Process in Reinforced Concrete Based on COMSOL Multiphysics

Reinforced concrete is deteriorated by chloride attack and dry-wet cycles to suffer serious durability problems. Reinforced concrete degradation typically occurs in two distinct stages: initially through chloride erosion, followed by the electrochemical corrosion of rebars. In this research, COMSOL Multiphysics was employed to model how various crack widths impact the degradation of reinforced concrete. Findings indicated that the deterioration process of reinforced concrete could be better simulated by COMSOL Multiphysics, and the degradation of reinforced concrete was significantly influenced by crack widths. As crack widths widen, chloride diffusion accelerated, leading to a rise in the corrosion current density of rebars. Notably, a crack width increased from 0.1 mm to 0.4 mm resulted in a 227.53% higher corrosion current density in rebars after 150 days of exposure. This study provides a theoretical basis for predicting reinforced concrete deterioration in the future.

Effect of local bond behavior degradation on tension stiffness in reinforced concrete with pre-existing longitudinal cracks

Reinforced concrete structures often have cracks when exposed to corrosion of rebars. This induced crack can deteriorate the bond capacity between concrete and rebar, affecting the structural performance of the member. This study conducted pull-out and uniaxial tension tests on cracked specimens to investigate the effect of bond behavior degradation on the tension stiffening effect. It uses an innovative approach to simulate concrete cracking by inserting an aluminum pipe into the concrete and filling it with an expansion agent to replicate the volumetric expansion caused by rebar corrosion. The local bond-slip behavior degradation is modeled using Popovics formulation based on pull-out cracked bond specimens. Furthermore, uniaxial tension tests reveal that induced cracks decrease transverse crack numbers and reduce the tension stiffening effect, primarily due to bond loss. However, this degradation becomes insignificant after a total deformation of 1.5 mm, corresponding to about 0.1% in average strain. Finally, analytical results confirm that tension stiffness does not necessarily decrease with increased induced crack width. Instead, the tension stiffness may increase in case of high bond loss due to induced crack.

A layer discrete particle based soft contact model in corroded rebar monitoring using linear and nonlinear ultrasonic guided waves

In offshore reinforced concrete (RC) structures, the phenomenon of rebar corrosion is widespread, seriously threatening the durability of the structures. However, the issue of rebar corrosion detection especially for the early corrosion situation is also challengeable. It is of great significance to use ultrasonic guided waves (UGWs) for monitoring the situation of the rebar corrosion entire process. In this paper, a mechanical model was used to establish the relationship between different rebar corrosion expansion states and layer-surface contact pressures in the layered RC components with radial cracks. Based on this model, a soft pressure-dependent contact 2D model in Abaqus was used to simulate the local corrosion layer. A linear and nonlinear signal joint analysis (LNSJA) method using PZT-based UGWs was proposed to monitor rebar corrosions, and an LNSJA-based rebar corrosion damage index (RCDI) for corroded RC components was proposed. The proposed method which can effectively detect both the micro- and macro-thickness as well as local area of rebar corrosion layer was validated by the relevant experiment and finite element analysis (FEA).